1. Field of the Invention
The present invention relates to an actuator latch of a hard disk drive to lock a magnetic head in a parking region in a magnetic head transfer mechanism of the hard disk drive.
2. Description of the Related Art
In general, as shown in FIG. 1, a hard disk drive includes a hard disk 20 and a magnetic head transfer mechanism. The hard disk 20, in which predetermined data is recorded, is rotatably installed on a base 10. The transfer mechanism transfers a magnetic head 50 to a desired track on the hard disk 20 to record and reproduce data. Here, the hard disk 20 is divided into a recording region 22 to record data and a parking region 21 on which the magnetic head 50 arrives when the rotation of the hard disk 20 stops. The magnetic transfer mechanism includes an actuator 30, a voice coil motor, and a latch. The actuator 30, in which the magnetic head 50 is installed, rotates around a rotating axis 34 on the base 10. The voice coil motor rotates the actuator 30 with an electromagnetic force. The latch locks the actuator 30 after the magnetic head 50 arrives in the parking region 21. The actuator 30 includes a suspension portion 31, an arm 32, and a bobbin 33. The suspension portion 31 suspends the magnetic head 50. The arm 32 is rotatably connected with the rotating axis 34. A movable coil 35 of the voice coil motor is wound around the bobbin 33 . The voice coil motor includes the movable coil 35 and a magnet 41, which is attached to the yoke 40 installed on the base 10 and generates a magnetic flux. The actuator 30 is placed between a pair of the yokes 40, not shown in FIG. 1. An electromagnetic force occurs due to the interaction between the magnetic force flux generated by the magnet 41 and current flowing through the movable coil 35. As a result, the actuator 30 rotates in a direction according to Fleming""s left-hand law. The latch locks the actuator 30 so that the actuator 30 does not move after the magnetic head 50 arrives in the parking region 21 as described previously. The latch includes a magnetic member 43, a damper 60, and an iron separation element 61. The magnetic member 43 is installed on the yoke 40 and magnetized by the magnet 41. The damper 60 is inserted into a combination protrusion 36 at the end of the bobbin 33 of the actuator 30. The iron separation element 61 is coupled to an end of the damper 60. Thus, if the actuator 30 rotates and the magnetic head 50 installed at the suspension portion 31 enters the parking region 21 of the hard disk 20, the iron separation element 61, coupled to one side of the bobbin 33, sticks to the magnetic member 43 as shown in FIG. 1. The actuator 30 remains locked due to the magnetic combination of the iron separation element 61 and the magnetic member 43 until the electromagnetic force to rotate the actuator 30 operates again.
The reason to lock the actuator 30 will be described below. The suspension portion 31 to suspend the magnetic head 50 provides an elastic force biasing the magnetic head 50 toward the horizontal plane of the hard disk 20. Thus, the magnetic head 50, to which an external force is not applied, keeps closely sticking on the horizontal plane of the hard disk 20. However, if the rotation of the hard disk 20 begins, air moves around the magnetic head 50 due to the rotation of the hard disk 20. The movement of air generates a lift force that lifts the magnetic head 50 from the horizontal plane of the hard disk 20. Thus, since the hard disk 20 is rotating when data is recorded on or read from the recording region 22 of the hard disk 20, the magnetic head 50 glides a predetermined distance above the horizontal plane of the hard disk 20. Thus, scratches due to the friction between the recording region 22 and the magnetic head 50 do not occur on the recording region 22. However, if the rotation of the hard disk 20 completely stops, as when power is turned off, the lift force that lifts the magnetic head 50 disappears. Thus, the actuator 30 rotates so that the magnetic head 50 is positioned in the parking region 21 before the lift force disappears. As a result, the magnetic head 50 safely arrives in the parking region 21, which is not related to recording and/or reproducing data, and thus does not have a bad effect on the recording region 22 although the lift force disappears as the rotation of the hard disk 20 stops. However, if the magnetic head 50 is pushed toward the recording region 22 due to an impact after the magnetic region 50 safely arrives in the parking region 21, the magnetic head 50 keeps touching the recording region 22 until the magnetic head 50 is lifted again when the hard disk 20 is re-driven. As a result, scratches may occur on the recording region 22. Hence, in order to solve this problem, the actuator 30 is locked using the latch so that the actuator 30 does not rotate although the impact is inflicted.
However, with this conventional latch, the actuator 30 is locked by a magnetic force which couples the magnetic member 43 to the iron separation element 61. Thus, the actuator 30 is unlocked if a force greater than the electromagnetic force is applied. Also, the actuator 30 is unlocked and begins moving because the electromagnetic force generated between the movable coil 35 and the magnet 41 exceeds the combination force due to the magnetic force between the iron separation element 61 and the magnetic member 43 to re-rotate the locked actuator 30. And, if the magnetic combination force between the iron separation element 61 and the magnetic member 43 is too small, the actuator 30 is easily unlocked even by a small impact. In other words, if the magnetic combination force between the iron separation element 61 and the magnetic member 43 is too small, the actuator 30 is easily unlocked even by a small impact. If the magnetic combination force between the iron separation element 61 and the magnetic member 43 is too great, the actuator 30 may not be unlocked even if the maximum electromagnetic force occurs to rotate the actuator 30. In the above-described structure, the actuator 30 springs out sharply due to inertia when the actuator 30 is unlocked by overcoming the magnetic combination force. Thus, the protrusion 36 may strongly crash against a stopper 42 opposite to the magnetic member 43. If the actuator 30 crashes against the stopper 42, head slap may occur due to the crash impact. Thus, to prevent the head slap, the application of current to the movable coil is controlled so that the actuator 30 is unlocked and supplied with a damping force. It is difficult to design a control system since the timing to unlock the actuator 30 and supply the damping force to the actuator 30 is accurately set. Also, due to repetitive locking and unlocking operations, the damper 60 is under continuous stress and it may be destroyed.
U.S. Pat. No. 4,692,829 discloses a locking structure adopting an aerodynamic latch member, not a locking structure by the magnetic force combination of an iron separation element and a magnetic member to inhibit a problem of head slap. In this locking structure, the aerodynamic latch member moves and an actuator is locked and unlocked due to wind occurring when a disk rotates. However, the sensitivity of moving the aerodynamic latch member must be accurate due to the strength of wind occurring when the disk rotates to prevent operation errors. Thus, an error in manufacturing and assembling the aerodynamic latch member should be minimized and a great burden is given in manufacturing the aerodynamic latch member.
Accordingly, it is an object of the present invention to provide a magnetic head of a hard disk drive having an improved structure to strongly keep an actuator locked and softly perform operations of locking and unlocking.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The foregoing and other objects of the present invention are achieved by providing an actuator latch of a hard disk drive to lock an actuator so that the actuator does not rotate when a magnetic head installed at the actuator driven by a voice coil motor is positioned on a parking region. The actuator latch comprises: a locking protrusion installed at the actuator; a latch member rotatably installed on the basis of a predetermined rotation axis, the latch member to rotate with the rotation of the actuator when the magnetic head is parked so that a hook intercepts the locking protrusion and prevents it from moving in an opposite direction to a parking side; and a latch member driving unit including a lever installed at the latch member to be joined with a yoke of the voice coil motor by a magnetic force when intercepting the moving path of the locking protrusion and a coil to form the same polarity as the yoke with current supplied by a power supply installed at the level, the latch member driving unit to rotate the latch member to set free the interception of the movement path of the locking protrusion by the hook.